SYCAMORE – William "Billy" Curl would be 71 years old when he gets out of prison under a plea agreement he's expected to accept today for the 2010 murder of college freshman Antinette "Toni" Keller.

DeKalb County State's Attorney Richard Schmack said the 37-year proposed prison sentence is the stiffest penalty negotiated in DeKalb County, except for a case that was eligible for the death penalty, since 1980. If finalized, the plea agreement would avoid a trial that could last for weeks and eliminate the possibility that Curl could be acquitted.

"Our job is to protect the public," Schmack said Tuesday. "We have Mr. Curl in jail. We believe he killed Antinette Keller. We believe very strongly about that. We want him to go to prison. That is not a sure thing when you go to trial. That is a sure thing when you plea it out."

Curl, 36, of DeKalb, was scheduled to stand trial April 11 on charges alleging he raped and murdered Keller, and then burned her body and her belongings. Keller, an 18-year-old Northern Illinois University freshman from Plainfield, was last seen about noon Oct. 14, 2010, when she told friends she was going for a walk in Prairie Park. Her burned remains were found in the park two days later.

Curl's public defenders and two prosecutors spent about 45 minutes Tuesday afternoon discussing details of the crime, potential sentences and a possible plea agreement in Judge Robbin Stuckert's private chambers.

"I am very comfortable with what we did," Schmack said. "Everyone in my office thinks this was a good result."

Curl accepted a stiffer prison sentence than prosecutors had once offered because he wanted a specialized plea, called an Alford plea, his sister Moria Curl said. In an Alford plea, the defendant maintains innocence but admits the evidence could convince a judge or a jury to find him guilty.

Keller's parents were not immediately prepared to comment Tuesday on the expected plea agreement and proposed sentence, according to family spokeswoman Mary Tarling, Keller's cousin.

Keller's parents, Diane and Roger Keller, drove about an hour from Plainfield to attend the Tuesday afternoon hearing, but arrived after the attorneys walked into the judge's chambers. They left before the attorneys returned from behind closed doors after learning no final action was expected Tuesday.

Her parents declined to be interviewed while at the courthouse.

Tarling said the concept of a plea agreement was sprung on Keller's family rather quickly, with the family learning of Tuesday's conference at the last minute. Schmack issued a two-paragraph news release announcing the expected 37-year sentence about an hour after the hearing concluded.

"The communication [with Schmack's office] has not been really strong," Tarling said.

Schmack said he and his staff spent 50 minutes on the telephone with Roger Keller on Monday reviewing the proposed agreement.

Moria Curl said her brother accepted the agreement out of hope of finishing his prison sentence before he died, but she believes in his innocence. Moria Curl emphasized that authorities do not know how Keller died, what time she died, or what weapon was used to kill her.

She said she believes the criminal justice system railroaded her brother, who initially cooperated with police but fled the county before a second scheduled police interview. He was arrested in Louisiana in late October 2010.

"He did leave out of state, and he did make a few bad decisions," Moria Curl said. "But that doesn't make him a murderer."